need circuit card for cordless phone?

where can i obtain the circuit card for a Vtech model DS6321 cordless phone, the received audio is weak, the battery is ok? I gave my set of 3 phones to a clergyman and one is bad, and I would like to fix it, probably all I need is a new circuit card which I can change, having been in the Electronics field, but been retire 20 some years ago.